Rapid Spectrophotometric Determination of Cerium in Cast Iron. (Determination of Small Amounts of Special Elements in Cast Iron, 7th Report)

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  • 鋳鉄中セリウムの光度定量法
  • チュウテツ チュウ セリウム ノ コウド テイリョウホウ

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Abstract

In the fluoride separation of cerium, the use of thorium possessing similar ionic radius as coprecipitant in the presence of NH4+ was introduced to the analysis of cast iron. The fluoride precipitate by this method is crystalline, so easy to handle in centrifugal tube, and moreover readily soluble in H3BO3 and H2SO4 mixture. The requisite time is shortened by eliminating the ignition of fluoride precipitate and successive dissolution by white-fuming with H2SO4 or HClO4, and also the procedure is more simplified. The fundamental conditions of fluoride precipitation and photometric procedure are investigated. In the fluoride precipitation the optimum amounts of reagents are 15 mL of H2SO4(6 N), 10 mg of Th, 10 mL of HF, and 10 mL of NH4OH in 100 mL of total volume. The amounts of H3BO3 and H2SO4 in the dissolution of fluoride precipitate give considerable effects on the absorbancy, and their optimum amounts at the color development are respectively 0.5 g and 5 mL in 80 mL of total volume. In the ultimate photometric determination, the absorbancy, is successfully measured at 320 mμ, and correction due to small amounts of adsorbed Fe3+ etc. can be made by decolorizing the developed Ce4+ alone with H2O2. The proposed method is suitable for determining 0.002∼0.1% of cerium in cast iron within about 1 hour.

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